"use client";

import { startTransition, useCallback, useLayoutEffect, useRef, useState } from "react";
import {
  parseRectificationCandidateResult,
} from "@/lib/rectification-candidate-result";
import {
  isAbortError,
  searchWindowFromSnapshot,
  caseStageFromSnapshot,
  interviewStopReasonFromSnapshot,
  interviewSessionOutcomeFromSnapshot,
  birthTimeSourceFromSnapshot,
  type RectificationCaseSnapshotPayload,
  type RectificationSnapshotFailure,
} from "@/lib/rectification-surface-state";
import type { RectificationTimelineStage } from "@/lib/rectification-timeline-scale";
import { isRectificationCaseStatus, type RectificationCaseStatus } from "@/lib/rectification-agentic/v9/case-status";
import { parseRectificationChoiceCard, type RectificationChoiceCard as ChoiceCardModel } from "@/lib/rectification-agentic/v9/choice-card";
import { snapshotTurns } from "@/lib/rectification-chat-messages";
import {
  caseSnapshotState,
  currentQuestionFromSnapshot,
  questionSourceFromSnapshot,
  type CandidateResult,
  type CurrentQuestionModel,
} from "@/lib/rectification-chat-snapshot";

/**
 * Case snapshot sync for the rectification chat surface: the state that the
 * persisted Candidate Snapshot API owns (candidate, current question, choice
 * card, saved time, timeline window / stage, interview outcome), the
 * question-recovery counters that reset when a question arrives, and the one
 * snapshot read in flight. Moved out of RectificationAgenticChat unchanged
 * (TASK-rectification-code-split-20260926).
 */
export function useRectificationCaseSnapshot({
  caseId,
  sessionId,
  initialSnapshot,
}: Readonly<{
  caseId: string;
  sessionId: string;
  initialSnapshot: RectificationCaseSnapshotPayload | null;
}>) {
  const [resultNotice, setResultNotice] = useState(initialSnapshot?.case?.result_notice ?? null);
  const [canRecompare, setCanRecompare] = useState(initialSnapshot?.case?.result_identity?.can_recompare === true);
  const [savedTime, setSavedTime] = useState<string | null>(() => caseSnapshotState(initialSnapshot)?.savedTime ?? null);
  const [savedStatus, setSavedStatus] = useState<"accepted" | "confirmed" | null>(() => caseSnapshotState(initialSnapshot)?.savedStatus ?? null);
  const [candidateResult, setCandidateResult] = useState<CandidateResult>(() => caseSnapshotState(initialSnapshot)?.candidate ?? null);
  const [choiceCard, setChoiceCard] = useState<ChoiceCardModel | null>(() => caseSnapshotState(initialSnapshot)?.choice ?? null);
  const [currentQuestion, setCurrentQuestion] = useState<CurrentQuestionModel | null>(() => caseSnapshotState(initialSnapshot)?.question ?? null);
  const [questionSource, setQuestionSource] = useState<"focus" | "unavailable" | null>(() => caseSnapshotState(initialSnapshot)?.questionSource ?? null);
  const [caseStatus, setCaseStatus] = useState<RectificationCaseStatus | null>(() => caseSnapshotState(initialSnapshot)?.caseStatus ?? null);
  const [searchWindow, setSearchWindow] = useState<readonly [string, string] | null>(() => caseSnapshotState(initialSnapshot)?.searchWindow ?? null);
  const [caseStage, setCaseStage] = useState<RectificationTimelineStage | null>(() => caseSnapshotState(initialSnapshot)?.stage ?? null);
  const [nextUserActionId, setNextUserActionId] = useState<string | null>(() => caseSnapshotState(initialSnapshot)?.nextUserActionId ?? null);
  const [interviewStopReason, setInterviewStopReason] = useState<string | null>(() => caseSnapshotState(initialSnapshot)?.interviewStopReason ?? null);
  const [interviewSessionOutcome, setInterviewSessionOutcome] = useState<string | null>(() => caseSnapshotState(initialSnapshot)?.interviewSessionOutcome ?? null);
  const [birthTimeSource, setBirthTimeSource] = useState(() => caseSnapshotState(initialSnapshot)?.birthTimeSource ?? birthTimeSourceFromSnapshot(initialSnapshot));
  const [caseSnapshotLoaded, setCaseSnapshotLoaded] = useState(initialSnapshot !== null);
  const [questionRetryAttempts, setQuestionRetryAttempts] = useState(0);
  const [questionRepairAttempts, setQuestionRepairAttempts] = useState(0);
  const [questionRepairing, setQuestionRepairing] = useState(false);
  const [snapshotFailure, setSnapshotFailure] = useState<RectificationSnapshotFailure | null>(null);
  const snapshotAbort = useRef<AbortController | null>(null);
  const currentQuestionRef = useRef(currentQuestion);

  useLayoutEffect(() => {
    currentQuestionRef.current = currentQuestion;
  }, [currentQuestion]);

  // Candidate snapshot comes from the persisted Candidate Snapshot API, never
  // from parsing agent text or hidden sentinels.
  const applyCaseSnapshot = useCallback((payload: RectificationCaseSnapshotPayload | {
    latest_result?: unknown;
    current_question?: unknown;
    choice_card?: unknown;
    step_state?: unknown;
    turns?: unknown;
    question_source?: unknown;
    next_user_action?: { id?: unknown };
    interview?: { stop_reason?: unknown; session_outcome?: unknown };
    case?: {
      status?: unknown;
      accepted_time?: unknown;
      confirmed_time?: unknown;
      candidate_range?: unknown;
      stage?: unknown;
    };
  } | null) => {
    if (!payload) return;
    const snapshot = payload as RectificationCaseSnapshotPayload;
    setResultNotice(snapshot.case?.result_notice ?? null);
    setCanRecompare(snapshot.case?.result_identity?.can_recompare === true);
    const nextCandidate = parseRectificationCandidateResult(payload.latest_result);
    const nextQuestion = currentQuestionFromSnapshot(payload.current_question);
    const nextChoice = parseRectificationChoiceCard(payload.choice_card);
    const nextCaseStatus = isRectificationCaseStatus(payload.case?.status)
      ? payload.case.status
      : null;
    const acceptedTime = typeof payload.case?.accepted_time === "string" ? payload.case.accepted_time : null;
    const confirmedTime = typeof payload.case?.confirmed_time === "string" ? payload.case.confirmed_time : null;
    const nextActionId = typeof payload.next_user_action?.id === "string"
      ? payload.next_user_action.id.trim()
      : "";
    // Only overwrite when the payload actually carries them: a snapshot without
    // a window should leave the timeline showing the last known one rather than
    // dropping to the skeleton mid-session.
    const nextWindow = searchWindowFromSnapshot(payload.case?.candidate_range);
    if (nextWindow) setSearchWindow(nextWindow);
    const nextStage = caseStageFromSnapshot(payload.case?.stage);
    if (nextStage) setCaseStage(nextStage);
    setCandidateResult(nextCandidate);
    setCurrentQuestion(nextQuestion);
    setQuestionSource(questionSourceFromSnapshot(payload.question_source));
    setChoiceCard(nextChoice);
    setCaseStatus(nextCaseStatus);
    setNextUserActionId(nextActionId || null);
    setInterviewStopReason(interviewStopReasonFromSnapshot(snapshot));
    setInterviewSessionOutcome(interviewSessionOutcomeFromSnapshot(snapshot));
    setBirthTimeSource(birthTimeSourceFromSnapshot(snapshot));
    setCaseSnapshotLoaded(true);
    if (nextQuestion || nextChoice || acceptedTime || confirmedTime) {
      setQuestionRepairAttempts(0);
    }
    if (confirmedTime) {
      setSavedTime(confirmedTime);
      setSavedStatus("confirmed");
    } else if (acceptedTime) {
      setSavedTime(acceptedTime);
      setSavedStatus("accepted");
    }
  }, []);

  const loadCaseSnapshot = useCallback(async (
    mergeMessages?: (turns: readonly unknown[]) => void,
  ): Promise<{
    question: CurrentQuestionModel | null;
    turns: readonly unknown[];
  } | null | undefined> => {
    snapshotAbort.current?.abort();
    const controller = new AbortController();
    snapshotAbort.current = controller;
    try {
      const response = await fetch(
        `/api/rectification/cases/${encodeURIComponent(caseId)}?sessionId=${encodeURIComponent(sessionId)}`,
        { cache: "no-store", signal: controller.signal },
      );
      if (controller.signal.aborted) return undefined;
      if (!response.ok) {
        setSnapshotFailure({ status: response.status });
        return undefined;
      }
      const payload = await response.json().catch(() => null);
      if (controller.signal.aborted) return undefined;
      const turns = snapshotTurns(payload);
      startTransition(() => {
        setSnapshotFailure(null);
        applyCaseSnapshot(payload);
        mergeMessages?.(turns);
      });
      return {
        question: currentQuestionFromSnapshot(payload?.current_question),
        turns,
      };
    } catch (error) {
      if (isAbortError(error) || controller.signal.aborted) return undefined;
      setSnapshotFailure({ status: "network" });
      return undefined;
    } finally {
      if (snapshotAbort.current === controller) snapshotAbort.current = null;
    }
  }, [applyCaseSnapshot, caseId, sessionId]);

  return {
    resultNotice,
    canRecompare,
    savedTime,
    setSavedTime,
    savedStatus,
    setSavedStatus,
    candidateResult,
    setCandidateResult,
    choiceCard,
    currentQuestion,
    questionSource,
    caseStatus,
    searchWindow,
    caseStage,
    nextUserActionId,
    setNextUserActionId,
    interviewStopReason,
    interviewSessionOutcome,
    birthTimeSource,
    caseSnapshotLoaded,
    questionRetryAttempts,
    setQuestionRetryAttempts,
    questionRepairAttempts,
    setQuestionRepairAttempts,
    questionRepairing,
    setQuestionRepairing,
    snapshotFailure,
    snapshotAbort,
    currentQuestionRef,
    applyCaseSnapshot,
    loadCaseSnapshot,
  };
}

export type RectificationCaseSnapshotSync = ReturnType<typeof useRectificationCaseSnapshot>;